1. Field of the Invention
This invention relates to electrical switching apparatus such as power circuit breakers, network protectors and switches used in electric power circuits carrying large currents. More particularly, it relates to such apparatus which utilizes a large spring to store sufficient energy to close the contacts of the apparatus against the sizeable magnetic repulsion forces generated by the large currents. Specifically, it relates to an interlock which prevents release of the close spring when the contacts are already closed, or simultaneously with actuation of a trip device which opens the separable contacts.
2. Background Information
Electrical switching apparatus for opening and closing electric power circuits typically utilize an energy storage device in the form of one or more large springs to close the contacts of the device into the large currents which can be drawn in such circuits. Such electrical apparatus includes power circuit breakers and network protectors which provide protection, and electrical switches which are used to energize and deenergize parts of the circuit or to transfer between alternative power sources. The close spring is charged either by a manual charging handle or an electric motor. The energy stored in the close spring is released to rapidly close the contacts by a push to close button on the circuit breaker switch or by a solenoid which may be remotely actuated.
Such power protection devices and switches also include an open spring or springs which rapidly separates the contacts to interrupt current flowing in the power circuit. As indicated, either or both of the close spring and open spring can be a single spring or multiple springs and should be considered as either even though the singular is hereafter used for convenience. The open spring is charged during closing by the close spring which therefore must store sufficient energy to both overcome the mechanical and magnetic forces for closing as well as charging the open spring. The stored energy in the open spring is released, again, either by an open push button on the apparatus, or by a solenoid which may be remotely energized.
Once the contacts have been closed, the close spring may be recharged to be ready for a subsequent closing. Since the contacts are already closed, it is known to provide an interlock which prevents discharge of the close spring while the contacts are closed. It is also known to provide an interlock which prevents simultaneous actuation of both the open push button and the close button. In other circuit breakers of this type, it is known to have an interlock which gives priority to the open button or solenoid so the circuit breaker can always be opened. While these interlocks have been effective, there is room for improvement.
There is a need in general for an improved interlock for electrical switching apparatus.
In particular, there is a need for an interlock which gives priority to opening the contacts of the electrical switching apparatus.
There is a further need for such an interlock which prevents release of the closing springs when the contacts are closed.